1. Field of the Invention
The invention relates to a method for the reduction of finely divided metal oxide material by treatment in the presence of carbonaceous material with a gas containing molecular oxygen.
The reduction of materials containing metal oxide, for example iron ore, may be carried out on the material in finely divided solid form in the presence of a carbonaceous material, for example coal, and to which oxygen and air are supplied. The oxygen effects a partial combustion of the carbonaceous material so that the necessary reaction temperature is achieved, while at the same time reducing gases necessary for the reduction process are formed. The reduction may be a pre-reduction, for example a reduction or iron ore into a product with a degree of metallization of from 50 to 80%. The pre-reduced product thus obtained is then subjected in a second stage to a reduction in molten form so that all metal oxide is reduced.
2. The Prior Art
When the reduction described above is utilized for pre-reduction of iron ore, it may suitably be performed at a temperature of around 800.degree. - 1100.degree. C and advantageously in a reactor in the form of a fluidized bed. Iron ore and the carbonaceous material are normally continuously supplied to the reactor, as well as the oxygen or the air, whereas the reduced iron ore and gases which have been in contact with the iron ore are removed therefrom continuously. The removed gases contain reducing substances, such as CO and H.sub.2, as well as oxidizing substances, such as CO.sub.2 and H.sub.2 O. The gases also contain N.sub.2 if air has been supplied to the reactor vessel. In order to utilize the contents of reducing substances in the gases, the contents of oxidizing substances may be removed in a washing plant and the remainder of the gases returned to the reactor. In connection with washing, the gas must be cooled to near room temperature and thereafter preferably be heated to temperatures in the vicinity of that of the reduction reactor. A washing plant for this purpose with supplementary devices for cooling and heating is very large.